Large quantities of liquids and similar materials are often stored in bulk storage containers or tanks, which may be located above-ground, partially above-ground, or completely below ground. Such containers or tanks are generally connected by piping to dispensers. For example, underground storage tanks (UST's) and, occasionally, above-ground storage tanks (AST's) are used to store petroleum products and fuel to be dispensed at automobile service stations, trucking terminals, automobile rental outlets, and similar operations through gasoline, diesel, fuel with biofuel constituents, or kerosene dispensing pumps.
Fuel product is generally delivered to such facilities by a gravity drop from a compartment in a wheeled transport means such as a fuel delivery truck. AST's or UST's are often located at central distribution locations so that product can be subsequently withdrawn from the tank system to be transported for delivery to a variety of such facilities. A distribution location with UST's or AST's may receive deliveries of product from, e.g., a pipeline spur, wheeled transport, a barge, or a rail car.
Direct observation of the operating condition of such tanks and storage containers is difficult or impossible. The various methods for identifying the amount of product in tank systems have varying levels of accuracy, repeatability, and performance. Moreover, the accuracy of devices which measure the amount of product dispensed from the storage containers and tanks differs greatly, and are often designed for infrequent measurement periods.
Consequently, effective management of such facilities is complicated by the numerous errors and time delay associated with the various measuring devices and procedures used to detect thefts, leaks, and other catastrophic failures.
Traditionally, these functions were performed crudely or, in many cases, not at all. Volume measurements were, and in many instances still are, based on imperfect knowledge of the geometry, dimensions, and configuration of the storage vessel. Also, dispensing meters are frequently miscalibrated. This is true even when the operation of tank systems is regulated, due to the breadth of tolerance permitted for individual sales as related to total tank volume.
There are numerous other instances of unregulated behavior at dispensing and storage stations. For example, fuel deliveries are almost always unmetered, additions of product from defueling vehicles are often not monitored, and theft of the product is not uncommon. In addition, many existing volume-based approaches are not suitable to the real-time or dynamic monitoring and inventorying of fuel product. Similarly, real-time monitoring of fuel intake, fuel leaks, fuel thefts, and other changes in fuel inventory had not been available. Generally, monitoring of fluid storage facilities is performed during quiet periods when no fluid is moving. Further, the time elapsed between these quiet periods is usually measured in terms of several hours or even days.
In addition, although there is extreme volatility in oil and fuel prices in the short term, the general projections for the future indicate that prices will only increase. The significant costs associated with purchasing fuel increases the incidence of theft at fueling stations. Further, since the trend is toward larger scale fuel stations that dispense large volumes of fuel per month, it is likely that the costs associated with theft of fuel will increase and that, when a leak occurs, a greater amount of product loss will remain undetected for long periods of time.
In order to combat theft, mitigate losses, and improve the speed which leaks are detected, a need exists for improved monitoring of fuel dispensing and storage systems.